It is known to superplastically form a workpiece by placing the workpiece in a die, within an autoclave, heating the die and workpiece up to a temperature at which the workpiece is superplastically formable and applying a pressure differential across the workpiece to superplastically form the workpiece to the shape of the die.
It is known from European patent application EP0703019A to superplastically form a workpiece using a laser to locally heat the workpiece up to a temperature at which the workpiece is superplastically formable and applying a pressure differential across the workpiece to superplastically form the workpiece to a required shape without the use of a die.
A problem with the above methods of superplastically forming a workpiece is that there is very little, or no, control of the thickness distribution of the resulting component or article.